Symptoms Verification

Before using the Symptom tables, perform the following inspections:

• Verify that the malfunction indicator lamp (MIL) is operating correctly. Use the scan tool to command the lamp ON and OFF.
• Verify that there are no DTCs that are stored.
• Verify that the scan tool data is within a normal operating range. Refer to Control Module References for scan tool information.
• Verify the customer concern.
• Perform the Visual/Physical Inspection in this section. The visual/physical inspection is extremely important, and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition.
• Verify that there are no bulletins for the current symptom.
• Verify that the vehicle tires are correctly inflated and meet original equipment specifications.

Identifying Intermittent Conditions 

Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movements of a component. Refer to the following for a list of issues that may cause an intermittent condition:

• Moisture and water intrusion in connectors, terminals, and components
• Incomplete connector mating
• Poor terminal contact
• High circuit or component resistance-High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
• Harness that is too short or tight
• Wire insulation that is chaffed or cut
• High or low ambient temperature
• High or low engine coolant temperatures
• High underhood temperatures
• Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load
• High or low system voltage
• High vehicle load conditions
• Rough road surfaces
• Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
• Incorrect installation of aftermarket, add on accessories

Visual/Physical Check

• Verify that the control module grounds are clean, tight, and correctly located.
• Verify that the vacuum hoses are not split or kinked, and are properly connected, as shown on the Vehicle Emission Control Information label.
• Verify that the air filter is clean and free from restrictions.
• Verify that there is no water intrusion in connectors terminals and components.
• Inspect the air intake ducts for the conditions listed below:
  • Collapsed
  • Damaged areas
  • Looseness
  • Incorrect installation
  • Leaking

    If any condition listed above has allowed non-metered air to enter the air induction system, the Q38 Throttle Body: Throttle/Idle Learn procedure must be performed after the repair is complete.

• Inspect for air leaks at the throttle body mounting area, the mass air flow (MAF) sensor and intake manifold sealing surfaces.
• Inspect the wiring harness for the following conditions:
  • Poor connections
  • Pinches
  • Cuts
• Inspect for loose, damaged, unseated, or missing sensors/components.
• Inspect the terminals for corrosion and correct contact.